There are a wide variety of applications which call for the inspection of objects to determine or verify their dimensions. For example, during or after the manufacture of an object it may be necessary to verify the object's dimensions for quality control purposes. Alternatively, it may be desired to determine an object's dimensions for reverse engineering purposes.
Automatic inspection systems which employ digital cameras are well known, especially for inspecting generally planar objects such as sheet metal or printed circuit boards.
The image data captured by a digital camera is created by projecting light in 3D onto a 2D sensor. A common way to resolve this information back into 3D data is to capture images from multiple view points. Multiple viewpoints can be achieved using multiple cameras, or by moving a single camera with a precision positioning device.
Alternatively some systems employ specialised optical equipment such as a telecentric lens or a line scan camera, to constrain the system so that 3D measurement data can be resolved from a single image.
One problem with conventional inspection systems of the type outlined above is that they are expensive. As a result, in many applications inspection is still performed manually using calipers or rulers.
It would be desirable, therefore to provide an inspection system which does not require multiple cameras, relative movement between the object and the camera, or specialized optical equipment